Aburaki et al. U.S. Pat. No. 4,406,899 discloses 7-[.alpha.-(2-aminothiazol-4-yl)-.alpha.-(Z)-methoximinoacetamido]-3-[(1-m ethyl-1-pyrrolidinio)methyl]-3-cephem-4-carboxylate in the zwitterion form and mentions corresponding acid addition salts (which are present in the zwitterion form in injectable compositions) and shows that the zwitterion form has broader spectrum activity than ceftazidime and cefotaxime.
However, the aforementioned Aburaki et al. cephalosporins are stable only for a few hours as injectable compositions and the zwitterion form even as a dry powder is unstable at room temperature and loses 30% or more of its activity on storage at elevated temperatures (e.g. 45 deg. C. and above) for even one week and therefore requires special insulated packaging and/or refrigeration and is at a packaging and storage disadvantage compared to ceftazidime and cefotaxime.
While Aburaki et al. mentions acid addition salts, the patent does not state how to make these or state which if any of these salts have good stability in dry powder form. Kessler et al., "Comparison of a New Cephalosporin, BMY 28142, with Other Broad-Spectrum .beta.-Lactam Antibiotics", Antimicrobial Agents and Chemotherapy, Vol. 27, No. 2, pp. 207-216, Feb. 1985 mentions the sulfate salt, but does not disclose how to prepare such or that this salt has room temperature stability and good elevated temperature stability in dry powder form.